1. Field
Embodiments of the present invention relate to an organic light emitting display and a method of driving the same.
2. Description of the Related Art
Recently, various flat panel displays (FPDs) capable of reducing the weight and volume that are disadvantages of cathode ray tubes (CRTs) have been developed. The FPDs include liquid crystal displays (LCDs), field emission displays (FEDs), plasma display panels (PDPs), and organic light emitting displays.
Among the FPDs, the organic light emitting displays display images using organic light emitting diodes (OLED) that generate light by recombination of electrons and holes. The organic light emitting display has high response speed, and is driven with low power consumption. In a common organic light emitting display, currents corresponding to data signals are supplied to organic light emitting diodes (OLED) using the transistors formed in each of the pixels so that the OLEDs emit light.
The conventional organic light emitting display includes a data driver for supplying data signals to data lines, a scan driver for sequentially supplying scan signals to scan lines, an emission control line driver for supplying emission control signals to emission control lines, and a display unit including a plurality of pixels coupled to the data lines, the scan lines, and the emission control lines.
The pixels included in the display unit are selected when the scan signals are supplied to the scan lines to receive the data signals from the data lines. The pixels that receive the data signals generate light components of brightness components corresponding to the data signals to display an image. Here, the emission times of the pixels are controlled by the emission control signals supplied by the emission control lines. In general, the emission control signals are supplied to overlap the scan signals supplied to one scan line or two scan lines to set the pixels to which the data signals are supplied to be in a non-emission state.
On the other hand, the organic light emitting display controls the brightness of a panel, that is, dimming while controlling the width of the emission control signals. Here, since the width of the emission control signals increases during dimming driving, when the pixels emit light once in one frame period, flicker noise may be generated. Therefore, during the dimming driving, a 2-duty driving method is used so that the pixels are turned on/off twice in the one frame period.
For example, the emission control signals supplied to the emission control lines E1, E2, . . . as illustrated in FIG. 1 to realize dimming are set so that emission is performed twice in the one frame period. However, in the 2-duty driving method, when a light-emitting region is set as a blank region in accordance with the emission control signals, the voltage value of a first power source ELVDD that supplies currents to the pixels changes so that noise in the form of horizontal stripes may be generated.
Describing the above in detail, a panel is divided into an active region and a blank region as illustrated in FIG. 2. In the active region, the pixels realize gray levels. In the blank region, no image is displayed. That is, the blank region does not emit brightness. During the manufacturing process, a plurality of scan lines and emission control lines are formed.
On the other hand, when the pixels emit light in the first region 1 and the second region 2 of the active region by the emission control signals, the first power source ELVDD is set as the voltage of a first voltage V1, as illustrated in FIG. 3. However, when a light-emitting region is positioned in the blank region by the emission control signals, that is, when only the first region 1 emits light in the active region, the first power source ELVDD is set as a second voltage V2 higher than the first voltage V1. That is, when a light-emitting region is positioned in the blank region by the emission control signals, the number of pixels that emit light is reduced, and the first power source ELVDD is set as the second voltage V2 higher than the first voltage V1 to correspond to low voltage drop. In this case, the brightness of the first region 1 positioned in the active region increases so that noise in the form of horizontal stripes may be generated.